Geometric distortion and the variation of plate scale across the detectors in WFC3 cause the pixel areas to vary across the field of view. Flat-fielding, assuming the flat-field is flat, effectively normalizes all pixels to the same area and subsequent surface brightness measurements can be done directly on the flt images. However, integrated photometry of point sources on the flt files will require a correction to restore the true relative pixel areas. This table provides that correction.

Both surface and point-source photometry can be done on drz files because the drizzling process removes the geometric distortion while keeping the sky flat.

*pam.fits files are not regular reference files and will only be accessible via this page, from the iref directory.

NOTE: The *pam.fits files have not yet been created, but will be listed here once available.